1. Make sure your local git username matches with your Gerrit username, Gerrit username needs to be configure in the Gerrit portal under settings -> HTTP Password
git config --global review.review.cyanogenmod.org.username "gerrit username"
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First, you need to start a topic branch. This 'branch' holds the changes you make to the files on your computer that you will ultimately send to the CyanogenMod servers for review. Create your topic branch:
repo start <branch name> <project path>
Now, you can cd to the project (directory) that contains the file(s) you want to edit:
cd path/to/project
Now you can make your changes. Make sure you do not edit any files before you run repo start, or your changes will happen on a different branch and will not be tracked correctly.
After you make your changes, you can commit them just as you would normally:
git add <file you edited>
git commit
ctop
(Same as moving to top/root of tree using cd)
Now you can upload your changes to the CyanogenMod server:
repo upload <project path>
That's it! Your change will be reviewed and may be accepted or rejected.